I. Field of Invention
This invention applies to the field of mechanical safe and arming devices used on fuzes. In particular, the invention herein involves a time delay latch mechanism located within the Arming Assembly of an arm fire device which is part of the delay fuze used in the U. S. Navy Mine Clearing program.
II. Background of the Invention
U.S. Navy is in the process of developing a Fuze, Delay for the Mine Clearing Program. Part of this Fuze is an Arm Fire Device, containing an Arming Assembly a portion of which is a Latch Mechanism. This latch mechanism must latch an 800 pound spring load and, upon certain time delay, release this load. The time delay mechanism is a mechanical run-away escapement having a one-half pound release force. This force has to unlatch the 800 pound load. To accomplish this, a force reduction mechanism, consisting of 31 components and a time delay mechanism, consisting of fourteen (14) components were used, totaling 44 components. The Time Delay Latch mechanism herein was designed to provide the requisite delay, to provide the desired latch release force and to reduce the number of parts.
Accordingly, it is an object of this invention to reduce the number of parts of the existing latch mechanism from 44 to 12. This alternative load release mechanism, whose preferred embodiment, is described herein consists of 10 components. The pyrotechnic time delay device consists of two components. This reduction translates into reduced costs of materials and manufacturing costs, thus providing significant savings to the U.S. Government.
Another object is to require less volume in the design envelope by locating the time delay latch mechanism with the Arming Assembly.
Yet, another object is to provide a latch release force of approximately 200 pounds which with a factor of safety of two, translates into 6000 phi of propellant force; more over the provided volume can deliver up to 10000 psi, if desired.
Finally, the last object is to provide a unique application of mechanical and energetic materials to achieve the objects described above.
It has now been discovered that the above and other objects of the present invention may be accomplished by the following mechanism and in the following manner.
The time delay latch mechanism is located within a ram shaft that holds a ram shaft spring captive between the ram shaft and housing. The latching mechanism for the ram shaft consists out of two ball detents located within the ram shaft and held in place by the housing. Ball detents hold captive a firing pin/detent which holds under compression a firing pin spring. A pyrotechnic timing and release element contains a primer, a pyrotechnic delay mix, and a propellant. The process is initiated with the release of the firing pin/detent propelled by the firing pin spring that will push the ball detents into the housing cavity thus locking the ram shaft in the cocked position. Pushing past the ball detents, the firing pin/detent at the same time will initiate the primer which in turn will initiate the delay mix which in turn will initiate the propellant to provide the pressure to push the firing pin /detent back and unlock the detents.